International Concrete Abstracts Portal

Following the strong earthquake in Chile on March 3, 1985, an intensive study was conducted to ascertain why the large inventory of moderate rise buildings in the coastal city of Vina del Mar performed so well during the earthquake. The major findings were that the vast majority of the buildings in this coastal city had a high wall area to total floor area ratio and that the reinforcement detailing in the boundaries of these walls were considerably less than required by U. S. codes. Analytical studies indicated that the high percentage of walls led to significantly lower drifts under severe seismic shaking, thus lowering the ductility demands on the walls. At lower levels of ductility demand, experimental results have demonstrated that wall boundaries did not need special detailing of transverse reinforcement. The findings from the series of research studies following the Chilean earthquake have led to modified U. S. design procedures that relate the need for special detailing in wall boundary elements to expected strain levels along the compression edge of the wall. The expected strain levels are determined based on the aspect ratio of the wall and the percentage of wall area to floor area used in the building.

An experimental program was carried out to investigate the behavior of concrete filled steel plate walls. Seven wall-panel specimens were tested under repetitive in-plane pure shear loading. Each specimen was made by connecting a pair of surface steel plates with partitioning webs and tie bars, and filling the boxes so-formed with concrete. The parameters investigated were the thickness of the surface steel plate, the number of partitioning webs and the presence or absence of headed stud bolts. Results describing a restoration force characteristic of a large loop area are presented. Rigidity after the onset of cracking approximates the cumulative value of truss rigidity (rigidity of resistance mechanism consisting of longitudinal and transverse tension chord members of steel plates and compression diagonals of concrete) and in-plane shearing rigidity of surface steel plates. The skeleton curve for the shear stress vs. shear strain relationship could be theoretically idealized into a quadri-linear curve with three control points.

SP-162 This fact filled symposium, developed in honor of Mete A Sozen, contains 17 highly informative papers. A spectacular addition to all reference shelves. This symposium took place at the ACI Fall convention in Tarpon Springs, Florida in October of 1994. The Sozen Symposium consisted of three sessions with eighteen speakers. The symposium and this SP volume were organized to permit Mete's students and colleagues to honor and thank him for his council and guidance during their studies at the University of Illinois.

Design algorithms expressed in current building codes and practiced in design offices focus attention on earthquake induced lateral forces and away from earthquake induced lateral displacements. These procedures have led to development of structural systems in which a portion of the structural frame is designed to resist the total seismic design force, while a substantial remainder of the structure is proportioned assuming it resists only gravity loads. This approach is commonly applied to design of slab-column systems in regions of high seismicity. For such systems, a displacement-oriented approach has advantages. Applications of the approach are described.

The objective of this paper is to present models for the design of confined masonry structures based on the available experimental data. In particular, this study deals with in-plane response of masonry walls subjected to lateral forces, with emphasis on aspects of initial stiffness, strength, and deformation capacity. The experimental information used in this work comprises tests performed at the Structures Laboratory of the Catholic University of Peru. Results indicate that stiffness can be calculated considering a wall cross section inertia using the transformed cross section concept with the appropriate moduli of elasticity for concrete and masonry. Bending strength can be estimated reasonably well, assuming for the cross section (1) a rectangular compressive stress distribution, (2) zero strength under tension, and (3) a linear strain distribution. Unit shear strength could be safely calculated as 0.5 f'm, where f'm is the characteristic compressive strength of masonry. It is observed that confined masonry can develop drift values larger than 0.5 percent of wall height, which is comparable to that of reinforced masonry. Deformation capacity is observed to increase for increasing wall horizontal reinforcement ratio and column horizontal and vertical reinforcement and to be reduced with increasing axial load.